Phenolic stabilizers and, in particular, alkylhydroxyphenyl-substituted esters, triazines and isocyanurates, are known to the art. The compounds are used to stabilize a wide range of materials and have particular utility as stabilizers for polyolefin polymers. (.beta.-aminoacrylyl) compounds are also known to the art (see U.S. Pat. No. 3,784,565, German Pat. No. 1,544,768, J. Amer. Chem. Soc., Vol. 67, Page 1017 (June, 1945), and Enka Biniiru, Vol. 10, No. 26 (1970) ). However, these materials are known for their ability to stabilize chlorine-containing polymers such as polyvinyl chloride, and are very poor stabilizers for polyolefinic polymers. Unexpectedly, it has been discovered that combinations of (1) phenolic compounds, particularly alkylhydroxyphenyl-substituted esters, triazines, or isocyanurates, and (2) (.beta.-aminoacrylyl) compounds, particularly bis(.beta.-aminoacrylyl) derivatives of cyclic and linear hydrocarbons, provide excellent stability for polyolefinic polymers.